Abstract

Locke is often credited with having refuted the Cartesian account of the identity of persons, which locates their identity in the identity of immaterial substance. J. L. Mackie speaks for many when he writes that “Locke makes out a strong case for both his negative theses, that personal identity is to be equated neither with the identity of a soul-substance nor with that of a man …”. I will argue here that Locke’s attack on the immaterial substance theory is, if viewed in the standard way, not only unsuccessful against the Cartesian theory but also unsuccessful even in its own terms. We will see, however, that Locke mingles this line of argument with another one which has not to my knowledge been remarked in the literature on Locke on personal identity; this line of argument is based on a deep agnosticism about the nature of thinking substance, and of substance generally, and it does succeed against a wide range of immaterial substance theories, but not, still, the Cartesian one. At the end of the paper I will make use of these results to sketch how two quite distinct strains of seventeenth-century thought about immaterial substance may be disentangled from each other. This should make us wary of the rather perfunctory characterizations of dualism, and particularly Cartesian dualism, which have been popular recently.